Hidden boxers:
Enter the following names to fight as that Character. To use the fighter in career and exhibition mode press Circle at the Pre-fight anking screen

Boxer - Code:

Q-Tip - Q TIP
O - O
Gargoyle - GARGOYLE
Jermaine Dupri - JERMAINE DUPRI
Mark Ecko - MARK ECKO
Marlon Wayans - MARLON WAYANS
Tim Duncan - TIM DUNCAN
Alien - ROSWELL
Clown - SHMACKO
Ed Mahone - ED MAHONE Hints:

Miniature boxers:
Enter the options screen and view the "Cyber Athlete" video sequence. Then, enter career mode and enter MINIME as a name to miniaturize all boxers. To return to normal size, enter RESETPASS as a name in career mode.

Throbbing boxer heads:
Enter THROB as a name at the boxer creation screen

Fight as Judge Mills Lane:
Enter the options screen and view the "Cyber Athlete" video sequence. Then, enter exhibition mode and intentionally get disqualified. Mills Lane will be unlocked as a middle weight boxer.

280 lb. Super Heavyweight fighter:
Select "Heavyweight" at first fighter attribute screen in career mode. Set the fighter's weight to "230" (maximum). Press X to go to second fighter attributes screen. Change the fighter's body style from "1" to "2". Press Triangle to return to first attributes screen, and the fighter's weight can now be set anywhere from 230 to 280 lbs.

Illegal kick:
Press Triangle + Circle + X + Square during a match to illegally kick your opponent in the midsection.

Get up faster:
Press Analog-stick Down + X after being knocked down to get up faster.

Career mode cheat:
You need to have 2 memory cards. one full and one with empty space to save your guy. Put the full card in slot one, nothing in slot two. Create a guy at the start to fight by doing this you are tricking the game into thinking you cannot save the guy so instead of fighting the computer for your career you are fighting fighters controlled by the player two controller. So you can fight in the career mode against your friends being your opposition. when you are ready to save your guy take the full card out and put the empty one in

Super Punch:
When your opponent is dazed, hold R1 + R2 util your opponent recovers. When he wakes up, release those buttons and you will unleash the super punch.

Illegal Moves:
Press R1 and R2 and any punch and you will do a illegal move but beware, too many will get you disqualified:

Triangle = head butt
Circle = kidney punch
Square = elbow
X = low blow